Power lines and childhood leukemia. This was big news in the 1970s, when epidemiologists found cancer clusters in neighborhoods near high-voltage power lines. In the late 80s, the New Yorker published a breakthrough series of articles bringing a human face to the issue.

Based on the epidemiology, it seemed like there had to be some kind of link. The problem was, scientists, working with cells and animals in laboratory experiments, couldn’t find a conclusive cause. And the issue fell off the proverbial radar screen, as the public became more concerned about cell phone radiation and brain tumors.

Granger Morgan and his colleagues at Carnegie Mellon University advised “prudent avoidance” in a series of booklets on the subject as well as articles in Spectrum. Basically, take reasonable steps to minimize risk, but don’t drive yourself nuts. That made sense to me; as part of research for an article I had my house tested for EMF (back in the day when my local utility would provide this service on request). After I found out the biggest emitter was the clock on the front of my stove, I had it disconnected (seemed prudent, I was pregnant at the time and cooked a lot). Then I pretty much forgot about it.

Until this week, when scientists from the Jiao Tong University School of Medicine in Shanghai announced the results of research that may finally explain just how EMF radiation causes childhood leukemia. Xiaoming Shen and his colleagues determined that the distribution of leukemia among children living hear high voltage power lines or transformers is not random; rather, it affects children carrying a certain genetic variantâ”that is, the ability to repair DNA breaksâ”vastly more often.

This simple sounding finding has huge implications. Researchers have long thought that EMF radiation caused DNA breaks, but couldn’t figure out how. Shen’s research points to a different mechanism; the EMF radiation doesn’t cause the breaks, but inhibits DNA repair, particularly in children that have a weakened repair mechanism to begin with.

A 2007 study led by Prof. Ray Lowenthal of the University of Tasmania and published in the “Internal Medicine Journal” established a link between its survey group of 850 Australians and adult onset of lymphatic and bone marrow cancers. Respondents who lived within 300 meters of power lines before the age of 5 reported five times the incidence of adult cancers; those who lived within that distance at any point up to age 15 were three times as likely to develop cancer.

Lowenthal allowed that his team’s results were suggestive rather than conclusive, noting that previous studies examined the short-term effects of living near power lines, and that additional studies, like his, assessing the long-term risks are needed.

Brain Cancer

The Centers for Disease Control and Prevention have compiled statistics relating to EMF exposure in the workplace as well as in the general environment, and determined that workers exposed to above-average levels of EMFs do report higher-than-normal cancer rates. The CDC stops short of establishing causation, however, noting that other factors not studied may be at play.

Studies compiled by the CDC show that workers exposed to greater than 4 milligauss, a unit of magnetic flux, showed increased rates of leukemia and brain cancers, though the inconsistency of cancer type makes conclusions difficult to draw. Additional data have shown a link to breast cancer and even a possible relationship to Alzheimer’s, but research in these areas is ongoing as of 2010.